Search

Copyright 2017 Electrical101.com All Rights Reserved.

Sitemap

Sitemap

Terms of Use

Electrical101

Test a 3-way Switch

  1. Turn off power to the switches at the circuit breaker and using a tester, make sure power is off. Remove the two 3-way switches so you can access the switch terminals. The wire connections do not have to be removed.
  2. Using a continuity tester, check continuity between the common (black) terminal and each of the traveler terminals (brass colored) of each 3-way switch.
  3. There should be continuity between the common terminal and only one of the traveler terminals. After toggling the switch, there should be continuity between the common terminal and only the other traveler terminal.

When a 3-way switch fails, there will usually be no continuity between the common terminal and one (sometimes both) traveler terminals of one of the 3-way switches.

Toggling 3-way Switch

Place leads of continuity tester on the common (black) terminal and one of the traveler (brass or silver) terminals

Place leads of continuity tester on the common terminal and the other traveler terminal

3 Way Switch Up Position 3-way Switch Down Position

Toggling 3-way Switch

Locate a Bad 3-way Switch

Usually when a 3-way switch fails, lights can be toggled on and off at one switch, but not the other. If one of the two 3-way switches toggles the light(s) on and off, the other 3-way switch has probably failed. Follow these steps to find which switch is bad.

  1. Toggle each switch until the light come on. Toggle one switch to see if it turns the light on and off. If it does, it is a good switch. Leave the light on.
  2. Toggle the other switch to see if it turns the light on and off. If it does, it is a good switch and the other is bad.

One of these switches will not turn the light on and off (while the light is on) and that is the bad switch.

Once you identify the bad switch, follow the steps below to verify it is bad and needs to be replaced.

Question or Comment?

How to Test and Replace a 3-way Switch Video

Switches are spring loaded to minimize arching and prolong their life. However, a very small amount of arcing is present when a switch is toggled. A bad switch may not fail completely, burned contacts may cause intermittent failure. Keep this in mind when troubleshooting switches. Intermittent failure could make troubleshooting difficult, especially with 3 and 4-way switches. If one 3-way switch needs to be replaced, the other one should be replaced too.

How to Troubleshoot Three-Way Switches

Line

Neutral

Line

Neutral

Black common wire is usually wrapped around the two traveler wires on a 3-way switch.

How to Test and Replace a 3-way Switch Video

Common wire wrapped around traveler wires.